'They have either distorted or evaded history by not mentioning what happened during the crackdown. There is no mention of the use of force, that military tanks and machine guns were used to disperse the crowds,' he said.

'This is deeply regretful. It is no different from changing 'Japanese invasion of China' to 'Japanese entry into China',' Mr Cheung said. 'Publishers are so worried their books will be banned and afraid of political pressure that they dare not tell students what really happened.'

The books will be on sale in bookshops before next term, but the South China Morning Post obtained advance copies of three of the five titles that will be available to schools. Exploring Chinese History, published by Ling Kee, gives the most detailed account over four pages. It describes the causes of the protests, including corruption and the growing divide between rich and poor, but does not mention that students were calling for democracy. It makes no reference to the violent crackdown, or the fact that unknown numbers of students, Beijing residents, and soldiers were killed when the military moved into the city centre.

The book's key author, Chan Hon-sum, who teaches history at CCC Kwei Wah Shan College, admitted having exercised self-censorship. 'I should have been more courageous in depicting the event. But as authors, we are all guessing the extent of control the government has over textbooks.' He said he would ask the publisher if he could add reference to the military crackdown.

Chinese History, published by Everyman's Book, mentions the event in two paragraphs. It says that 'on June 4, the government pacified the student movement' and then goes on to describe the emergence of the third generation of leadership.

Hong Kong Educational Publishing's New Concept Chinese History also makes no reference to the military action and resulting casualities, but says the government learned from the incident by paying more attention to the development of the political system.

While the Central Government said in 1989 a dozen people - mostly soldiers - were killed on June 4, estimates by non-government groups and media vary from several hundred to thousands.

The textbooks were written for the new Chinese history curriculum for Form Four and Five students, to be introduced in September. For the first time the curriculum covers developments up until the end of the last century. The previous one ended in 1976.Curriculum guidelines do not specify how the events of 1989 should be taught, but the recommended focus is on the country's growing diplomatic ties with the international community.

Chief curriculum development officer Lee Chin-hung said the Education and Manpower Bureau gave no directives on what should be written in the books. 'For politically sensitive issues, our guideline is they should be presented in a balanced, objective manner, and leave much room for students to form their own views.'

He dismissed accusations that the lack of reference to casualties amounted to distortion. 'Our main job is to see if there are inaccuracies in the texts, and we respect authors' professional judgment about what should go in. We cannot issue guidelines for every event in 5,000 years of Chinese history.'

Mr Cheung said the PTU would issue its own Chinese history teaching materials featuring video footage, the mainland government's version of the event and that by Ding Ziling, founder of the Tiananmen Mothers' advocacy group, whose son was killed.